Java 8 Coding Interview Questions | Asked In Many Interviews

 Q 1) Given A List . Write Java 8 Program to find Out 1st Element From List?

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import java.util.Arrays;

import java.util.List;

public class FirstElementOfList {

    // Given a List. Find First Element From the List

 

    public static void main(String[] args) {

       

           List<Integer> list=Arrays.asList(10,15,24,7,24,74,10,7);

           list.stream().findFirst().ifPresent(System.out::println);

    }

}

Q 2) Given A List ? Find Out the Count of All Element In A List?

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import java.util.Arrays;

import java.util.List;

public class TotalNumberOfElements {

    public static void main(String[] args) {

        List<Integer> list = Arrays.asList(10, 20, 30, 40, 50, 60, 70);

        long count = list.stream().count();

        System.out.println("The Total Number Of elements in list:" + count);

    }

}

Q 3) Use map() method of Stream API for Converting String Object into Uppercase.

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import java.util.stream.Stream;

public class StringObjUppercase {

    // Use map for converting String Object Into UpperCase In Java

    public static void main(String[] args) {

        String str[] = {"aa","bb","cc","dd"};

       

        Stream<String> stringStream=Stream.of(str);

        stringStream.map(String::toUpperCase).forEach(System.out::println);

    }

}

Q 4) Write A Java 8 Program to find out All Character Occurances In A String.

import java.util.Arrays;

import java.util.LinkedHashMap;

import java.util.Map;

import java.util.function.Function;

import java.util.stream.Collectors;

import java.util.stream.IntStream;

public class StringCharOccurnace {

    public static void main(String[] args) {

       

        String str = "Welcome To Bikkad IT";

        IntStream intStream=new String(str).chars();

        Map<Character, Long> characterFrequnecyMap=intStream.mapToObj(c -> (char)c).map(Character::toLowerCase).

        collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));

        characterFrequnecyMap.forEach((key, value) -> System.out.println("Character :" + key + " , Occrances :" + value ));

       

   

}

}

Q 5) Write A Java 8 program to sort the elements?

import java.util.Arrays;

import java.util.List;

public class SortIntegers {

   

// Given List Of Intgers. Sort the all values inside the list

   public static void main(String[] args) {

    List<Integer> list=Arrays.asList(10,15,24,7,24,74,10,7);

    list.stream().sorted().forEach(System.out::println);

   

   }

}

Q 6) Write A Java Program To Sort A List In Reverse Order.

import java.util.Arrays;

import java.util.Collections;

import java.util.List;

public class SortInReverseOrder {

    // Given a List Of Integers. Sort them According to Descending order.

    public static void main(String[] args) {

        List<Integer> list = Arrays.asList(10, 24, 17, 42, 6, 13, 20);

        list.stream().sorted(Collections.reverseOrder()).forEach(System.out::println);

    }

}

Q 7) Convert An Array Into Stream And Print the All Elements From Stram.

import java.util.Arrays;

public class SortArray {

    // Take an Array and Sort this array and then Convert this array into Stream.

    public static void main(String[] args) {

        int arr[] = { 10, 22, 12, 75, 2, 4, 9 };

        // Sorted the Array Using Parallel sort

        Arrays.parallelSort(arr);

        // Converted into a Stream and then printed Using forEach

        Arrays.stream(arr).forEach(n -> System.out.print(n + " "));

    }

}

Q 8 ) Given A String is There. You want To Find Out First Repeated Character From The String?

import java.util.LinkedHashMap;

import java.util.function.Function;

import java.util.stream.Collectors;

public class RepeatedCharacterInString {

    // Given String is there. Find Out the First Repeated Character in the String.

    public static void main(String[] args) {

        String str = "Welcome To Java";

        Character result = str.chars().mapToObj(c -> Character.toLowerCase((Character.valueOf((char) c))))

                .collect(Collectors.groupingBy(Function.identity(), LinkedHashMap::new, Collectors.counting()))

                .entrySet()

                .stream()

                .filter(entry -> entry.getValue() > 1L)

                .map(entry -> entry.getKey())

                .findFirst()

                .get();

        System.out.println("The First repeating Character in java:" + result);

    }

}

Q 9) Given A List Of Numbers. Find Out the Numbers Which are Starts With 1.

import java.util.Arrays;

import java.util.List;

public class NumbersStartsWith1 {

    // Given list of numbers. Find Out the Numbers which are starts with 1

    public static void main(String[] args) {

       

         List<Integer> list=Arrays.asList(10,24,17,42,6,13,20);

         // Consider this list. Find out the Numbers which are starts with 1

         list.stream().map(n -> n + "").filter(n -> n.startsWith("1")).forEach(n -> System.out.println(n));

    }

   

}

Q 10) Find Out the Maximum Number From A List?

import java.util.Arrays;

import java.util.List;

public class MaxNumberFromList {

    public static void main(String[] args) {

        List<Integer> list = Arrays.asList(10, 20, 30, 40, 50, 60, 70);

        Integer max_num = list.stream().max(Integer::compare).get();

        System.out.println("The maximun number from list: " + max_num);

    }

}